The present invention relates to a plasma processing apparatus for processing a processing object wafer mounted on a sample stage arranged in a processing chamber inside a vacuum chamber by using plasma formed in the processing chamber, and in particular, to a plasma processing apparatus including an electrode for electrostatically attracting a wafer onto a sample stage.
Plasma etching is widely used in a process of manufacturing semiconductor devices such as DRAMs and microprocessors. As one of problems of processing semiconductor devices by using plasma, reducing the number of dust particles (hereinafter also simply called dust) attaching to a wafer is cited. If dust particles attach onto a fine pattern in etching of a semiconductor device, the etching is locally blocked at that part, causing a pattern defect such as disconnection and a short circuit.
In order to prevent this, various measures to reduce the number of dusts attaching to a wafer have been devised in the past. For example, means to reduce the quantity of dusts attaching to a wafer is broadly divided into means to reduce the quantity of dusts peeled off from an inner wall of a processing chamber and means to prevent dusts that have been peeled off from the inner wall from dropping onto the wafer by appropriately controlling transportation of the dusts in the processing chamber.
Especially, as for the latter means, it is effective to actively control transport of the dust particles that have gas viscous force or are charged by using electrostatic force. On the other hand, as described in JP-A-2013-229445, in order to prevent charged dusts from coming close to a wafer, it is devised to make potential of the wafer (or relative potential to a component in the processing chamber) zero so that electrostatic force will not work between the dusts and the wafer.
As an example of such a conventional technique, a technique disclosed in the IP-A-2013-229445 is known. The conventional technique discloses a configuration to apply voltage to a focus ring of an electrostatic chuck which is arranged in a processing chamber and on which a substrate W to be processed is mounted before carrying the substrate W to be processed into the processing chamber so that potential difference between the focus ring and the substrate W to be processed which is carried into will be small. The conventional technique is a technique, by such a configuration, to try to prevent fine particles which have attached to the focus ring due to potential difference between the focus ring and the substrate W to be processed from moving and attaching to an upper surface of the substrate W to be processed.